I've reposted this same issue with a slightly different title than I had used before (so it wouldn't count as the same subject) using the one OS X system I've left Firefox 4.0 installed on. I've done this because I originally posted about my Mac problems from a Windows system, which still has Firefox 3.6 installed. Doing so caused this issue itself to be tagged as a Firefox 3.6/Windows 7 issue, which is entirely wrong!

Your posting system shouldn't assume that people are using the same system to post from as they are reporting issues about. The issue they're reporting could even be so bad that it's impossible for them to post with the same system.

I just downloaded Firefox 4.0 and I have exactly the same problem. The main applet on my web site (http://www.malinc.se/math/ ) flickers terribly on Mac OS X version 10.6.6. The only browser that displays the applet without flickering is Safari. Other applets flicker as well, but this one is the worst (due to the calculations making up the animation).

Some Mac users have reported problems with Firefox 4 on certain sites that use Java.

Firefox 4 runs as a 64-bit application on Mac OS 10.6 "Snow Leopard" by default. Try running Firefox in 32-bit mode, as follows:

1. Close Firefox (From the menu bar, select Firefox and then select Quit Firefox) .
2. Open the Applications folder in Finder (you can do that from the Dock) and locate the Firefox application icon.
3. Hold down the control key while you click the Firefox icon and select Get Info from the list of menu items.
4. In the "Firefox Info" window, click the box in front of "Open in 32-bit mode" so that it is checked.
5. Close the "Firefox Info" window and then restart Firefox 4.

Does that help?

From what I've heard, Java issues on Mac OS X will be fixed soon so you may not have to use this workaround after the next Firefox 4 update.

32-bit mode didn't help http://www.skyviewcafe.com/skyview.php at all, unfortunately.

Sorry it didn't help.

The Firefox 4 release notes (under Known Issues) mentioned running in 32-bit mode as a workaround for a Java issue, Firefox on Mac OS X running in 64-bit mode does not recognize that Java supports certain MIME types. Running Firefox in 32-bit mode has been found to help (see bug 638171)
...but looking through that bug report, it seems to be a different issue.

If I find out anything else I'll post it to this thread.

Bug 638171 looks like a very different issue from what I'm reporting here. None of the problems I'm seeing are related to a failure of MIME types to be recognized. The applet actually runs reasonably well with a hack (which I hope only has to be temporary) that launches the main interface for the applet in a separate window. Even there, the new window annoyingly appears behind the browser window instead of in front of it.

That hacked-up separate window, once you bring it forward from its hiding place behind the browser window, doesn't suffer from any of the high CPU usage, flickering, and 20-30 second input response lag problems that the applet suffers from when it tries to run within the browser frame. There is no difference in resources used or their MIME types. The problems here seem very much a matter of how the Java plugin shares the graphical environment with the browser when both try to operate within the same window.

Someone posted a topic today to the Apple support forums which you may want to add your input or watch for replies:

http://discussions.apple.com/thread.jspa?messageID=13296008&#13296008
Topic : OSX 10.6.7 Java Update causing massive slowdowns in Chrome 10 and Firefox 4
Posted: Mar 27, 2011 6:12 PM
Quote:
Since the 10.6.7 update, which included the recent Java RE update (1.6.0_24), I am seeing a massive slowdown for SOME java apps - the ones running out of Chrome (10.0) and Firefox (4.0).

Specifically, ADP's Enterprise Etime (a popular online time sheet system in use by a lot of Fortune-500 enterprises, including my employer) has slowed to a crawl: screen repainting literally runs at 1/100th (!) the speed I am used to: 10 secs to repaint a screen that normally takes 0.1secs to repaint when scrolling!

There are also serious problems with mouse events. Mouse hover and drag-n-drop events are not work anymore in FF 4.0 on Mac. In FF 3.6 they worked. You can test this on http://demo.aurigma.com/ImageUploader7/BasicDemo/Default.aspx

About the drag and drop problem, I found the bug in bugzilla and post a reply with your demo applet.

https://bugzilla.mozilla.org/show_bug.cgi?id=588455

You can vote for it if you want to see it fixed faster.

I have tried 32-bit, and it doesn't help much. I have tried safe mode too. I tried repair disc permissions (in Mac utilities), and it will repair, but the next time I run it, there is more to repair. It seems that the new Firefox update might be doing something to the operating system (10.6.7). In any case, I have had to repeatedly force quit Firefox. I had no trouble with it until I downloaded Firefox 4.0.1 for Mac. I really hope they can fix this quickly. I am concerned that continuing to use Firefox until this is corrected could permanently damage my computer. And I hope it will be advertised somewhere so that I won't actually have to be running Firefox to find out that the update is available -- since, really, I can't. Thanks.

Drag and drop in Java applets no longer work in Firefox 4. Would love to see this fixed. It seems the same issue applies to the latest version of Chrome. But Safari and IE are working fine...

DND in Firefox on Mac still not working..

Is anybody at mozilla / firefox team working on this issue? Or is it considered an obsolete solution to be replaced by html 5 or something ??

Incredibly annoying for those of us that are stuck with the applet way of uploading because of additional requirements...

A fix or a work-around to get this standard functionality of Java applets also working in Firefox 4 and 5 would be greatly appreciated...

Does anybody know the reason why Firefox stopped supporting this? Or at least why it does no longer work?

With Java 1.6.0_26 on OS X (tested on Snow Leopard, not yet tested on Lion) Java applet performance has improved, at least for the one applet I'm most concerned about. There's still an inexplicably high CPU usage, but my applet is far more usable. Safari performance is still better, however, with much more modest CPU usage.